Should the cable manager go above or below the patch panel?

Either position can be correct.

Put the manager above or below the patch panel according to where the cables actually need to travel and which arrangement produces the cleaner bend into the ports.

Rack layouts are full of local peculiarities — switch position, vertical management, cable entry and port density all matter more than a ceremonial rule about which side of the panel a manager ought to occupy.

Follow the cable path rather than a ritual.